Light bulb



FIG. 1 is a perspective view of the light bulb, with the broken line showing for illustrative purposes only and forming no part of the claimed design;

FIG. 2 is a first side elevational view of the light bulb;

FIG. 3 is a second side elevational view of the light bulb.

FIG. 4 is a top plan view of the light bulb; and,

FIG. 5 is a bottom plan view of the light bulb. 

The ornamental design for a light bulb, as shown and described. 